The present invention relates to pedometer devices, ie. devices which may be carried by a human subject for indicating the distance travelled on foot. The body of a subject walking or running undergoes a cyclic motion synchronised with the steps taken and, by responding to such motion a pedometer provides a count of the number of steps taken. This count may be displayed as such or in the form of a distance-travelled reading. In the latter case arrangements may be made for setting the instrument to suit the step-length of the particular subject.
An object of the present invention is to provide an improved pedometer device which is readily settable to suit the step-length and which may be constructed primarily from electronic components. Another object is to provide a pedometer device of such small size that it may be worn on the wrist in the manner of a wrist watch. A further object is to provide a pedometer device which may be housed within a wrist watch, eg. an electronic wrist watch, the power battery of which also serves to power the pedometer.
A further object is to provide an instrument which can be worn upon the wrist and actuated to give a display showing elapsed time, or a display showing distance covered on foot, as required.
A still further object is to provide a pedometer device which comprises
(a) a battery-powered electrical circuit having an output,
(b) a motion-sensitive modulator responsive to motions accompanying foot motions of the subject during said travelling to modulate said output and thereby provide discrete output signals, the number of which is a count of the number of said motions,
(c) a read-only memory device presettable to provide a numerical value corresponding with the distance to be travelled by the subject for each one of said motions,
(d) an electronic processor responsive to said output signals and to said read-only memory device to generate a distance signal representing the distance travelled by the subject, and
(e) a visual display for said distance signal.
The said motions accompanying foot motions of the subject may be motions at any part of the body. They may for example, be leg motions, motions in the region of the waist or arm motions, arm motions monitored at the wrist being preferred as conducive to convenience in use. Some forms of travel on foot, for example jogging, involve pronounced arm motions related to the foot motions. It is within the scope of the invention for the modulator to be responsive to pronounced arm motions but not sensitive enough to be responsive to the less pronounced motions occurring elsewhere, eg. at the waist.
Various forms of motion-sensitive modulator may be employed. A preferred form of modulator is an inertia switch and in a preferred arrangement, the modulator is an on-off inertia switch and said circuit has a resistor in series with said inertia switch, and said processor is sensitive only to output signals of magnitude comparable with such output signals as would be obtainable by by-passing said inertia switch. In this way, minor motions such as motions produced during rest periods and producing only light, high resistance, closure of the inertia switch are ignored in the distance indication. A preferred form of the inertia switch, provided as an aspect of this invention, is a mass loaded electrically conductive resilient member and an electrically conductive contactable member positioned so as to be normally out of contact with said resilient member but contactable by said resilient member on reaction thereof to said motions. The contactable member is preferably configured to surround said resilient member, eg. being of hollow cylindrical configuration with the resilient member normally projecting substantially centrally therethrough. In this way, directional discrimination, which could cause miscounting is minimized.
For ease of presetting, the read-only memory (ROM) may be provided in the form of a bank of on-off switches. The two possible positions of each switch represent the two possible values, 0 and 1, of a digit in a binary numerical system and each combination of on-and off positions of the switches provides a binary number stored by the ROM. Short-circuiting plugs can be used in place of the switches but are unsatisfactory in that they are too small for convenient handling and readily lost.
Simplicity is achieved, according to another aspect of the invention, by (1) having the ROM presettable to provide a numerical value which is an inverse function of the distance to be travelled per unit motion by the subject (2) providing a counter arrangement responsive to the output signals from the modulator to produce a distance sub-unit each time the number of discrete output signals provided by the modulator is a predetermined integral multiple of the numerical value and (3) providing visual display means arranged to be incremented by the distance sub-unit signals and indicate the distance travelled.
A convenient example of an inverse function as aforesaid is the number of steps to be taken by the subject to travel a distance sub-unit of 50 feet. For most purposes, a distance display in miles and tenths thereof travelled (ie. a display to one place of decimals) is adequate and it is better to use the figures available for display to indicate miles rather than hundredths or thousandths of miles. Such fine measurements would be of doubtful utility even if they were accurate. A three digit display is better used for indicating a distance of from 0 to 99.9 miles than a distance of from 0 to 9.99 miles or 0 to 0.999 miles. The preferred smallest unit to be measured is 0.1 mile. Given 20 steps per 53 feet as a possible step rate, 0.1 mile involves 200 steps. This number requires 8 bits to represent it in binary notation. To be of reasonably wide utility in allowing for shorter steps, 9 bits are required.
A 9 bit ROM would give far finer settings than are required. A smaller ROM is cheaper, easier to set and a 7 bit ROM is chosen in practice as giving an at least adequate range of settings. According to a further aspect of the invention, a binary digital counter is provided to count the discrete output signals from the modulator and the apparatus is so arranged that the least significant bits are ignored. For example, there is provided a comparator operable to pass a distance sub-unit for incrementing the visual display and resetting the counter to zero when the count, ignoring the two least significant bits, coincides with the number stored in the ROM.
This arrangement is readily constructed using parts which are commercially available as standard products of minute size. It lends itself well, as does the form of modulator hereinbefore described, to mounting within the case of an electronic wrist watch together with the timing parts. Although distance travelled on foot is the product of the number of steps and the step length, the provision of multiplying apparatus is avoided.